The original purpose of the invention was to thaw without cooking, raw frozen protein such as meat, fish and fowl.
The salient conditions for this fast thaw process are:
1. The food should have a slab-like form with a thickness which preferably does not exceed 11/8 inches.
2. The frozen food should be supported horizontally in a chamber with openings in the top and bottom walls of the chamber in the form of apertures, deflectors, or other guidance means for directing the flow of a gas.
3. A homogeneous saturated mixture of water vapor and air should be produced external to the chamber with a mixture temperature and dewpoint in the range of 140.degree. to 150.degree. F, if highest food quality is required. For maximum speed of thawing with acceptable food quality, a mixture temperature in the range of 160.degree. to 170.degree. F should be used.
4. The homogeneous mixture should be forced to flow turbulently through the openings in the chamber walls with components of the flow which are normal to the top and bottom surfaces of the frozen food supported in the chamber.
The apparatus of the invention is unique in that it has three forms. The first form produces the saturated mixture required for thawing without cooking frozen proteins such as steaks, chops, chicken, etc. This form employs an enclosure with at least one opening for controlling the temperature of the aeriform gases which are mixed with the steam. The position of the opening is remote from the source of the hot gases. A second form of the apparatus also employs an enclosure with an opening and the position of this opening is adjacent to the source of hot gases. The third form of the apparatus does not employ an enclosure.
The reconstitution of frozen cooked foods requires the use of either the second or third forms of the apparatus. The salient conditions for the reconstitution process require in the first place the conditions for the fast thaw process stated above with the exception of condition 3. The need for preheating the thawing chamber which is desirable in the case of the fast thaw process is mandatory for the reconstitution process.
The reconstitution of frozen food such as a TV dinner is best accomplished by using a homogeneous mixture of water vapor and an aeriform gas wherein the preferred mixture temperature has a range of 350.degree. to 425.degree. F and the preferred mixture dewpoint has a range of 140.degree. to 150.degree. F.
The new principle convective system preferably employs eight to 15 turbulent jets impinging on the top and bottom surfaces of domestic size food portions.
The speed of reconstitution is five times as fast as a domestic kitchen range oven with four TV dinners.
A first object of the invention is to thaw, without cooking, frozen proteins such as steak, chops, chicken, etc.
A second object is to reconstitute frozen prepared food.
The fundamental and unique feature of the present invention is heat transfer from a homogeneous superheated mixture which is substantially higher than the mixture dewpoint to a food when the food temperature is above the dewpoint of the gaseous mixture. The homogeneous mixture will be defined to be a vapor aeriform gas. An aeriform gas is usually air or a mixture of air with gas burner products.
A major feature of the invention is a radically new principle forced convection system which provides a serving temperature distribution throughout a homogeneous food with a temperature variance of only a few degrees.
This invention also teaches the production of a vapor aeriform gas by transforming a portion of the sensible heat of a gas flame into the latent heat of water vapor, and then mixing the gas products with the water vapor.
Another object is to reduce the loss of moisture from the food during the reconstitution process.
A further object is to prevent charring or discoloration of the food during reconstitution.